The natural crystalline lens of the eye plays a primary role in focusing light onto the retina for proper vision. However, vision through the natural lens may become impaired due to an injury, or due to the formation of a cataract caused by aging or disease. To restore vision, the natural lens is typically replaced with an artificial lens. An artificial lens may also be implanted to make a refractive correction.
Many surgical procedures have been developed for removing the natural lens. Typically, a slender implement is inserted through a small incision in the eye to contact the natural lens. The implement includes a cutting tip that is ultrasonically vibrated to emulsify the lens. The emulsified fragments of the lens are then aspirated out of the eye through a passage provided in the cutting tip. The slender nature of the implement enables extraction of the lens through a small incision in the eye. The use of a small incision over other procedures requiring a large incision can lessen the trauma and complications experienced during the surgery and postoperatively.
Because the incision required to remove the lens is small, the development of intraocular implants to replace the lens has been in the direction of flexible implants that do not require any enlargement of the incision. An intraocular lens commonly includes a generally disk shaped optic which focuses light on the retina and an outwardly extending haptic portion for proper positioning of the optic within the eye. The flexible nature of the lens enables the lens to be folded and compressed so as to occupy a smaller cross-sectional area for passage through the narrow incision and into the eye. Once inserted through the incision, the lens is permitted to expand to its original size and shape.
A number of devices have been developed to insert a flexible intraocular lens through a small incision in the eye. For example, U.S. Pat. No. 4,681,102 to Bartell uses a hinged cartridge which closes about a lens to fold the lens into a narrower configuration. The cartridge is placed into an inserter mechanism which advances the folded lens into the eye. The inserter, however, requires several components to be manipulated and assembled during the operation. U.S. Pat. No. 5,275,604 to Rheinish et al. pushes the lens through a narrowing lumen formed with grooves which act to fold the lens into a smaller size as it is pushed toward the eye. The manufacture of spiraling grooves in a tapering lumen is difficult if not impossible to accomplish in a practical manner. In U.S. Pat. No. 5,304,182 to Rheinish et al., a curling member is shifted laterally to fold the lens into a size small enough to pass through the narrow incision. However, no locking arrangement is provided to ensure completely closing of the curling member.
Moreover, while these devices function to reduce the cross-sectional size of the lens for insertion into the eye, they all require the opposing side edges of the lens to be folded over on themselves in order to fit through the narrow incision. As a result, the lens must swing open within the eye to regain its original shape and size. Such unfolding causes the lens, and particularly the haptic, to be swung in an arc, and thus risks damaging the interior of the eye.
As the lens is released into the eye, the resiliency of the lens causes the lens to open and resume its natural shape. However, the folding and pressing of the lens needed to pass the lens through the small incision places a significant amount of inward pressure on the lens. As a result, the lens is frequently discharged from the inserter with considerable force and velocity. This forceful, uncontrolled release of the lens also places the interior of the eye at risk of being injured.
Further, many inserters do not maintain control of the orientation of the lens as the lens is advanced into the eye. Consequently, the lens may rotate or turn about a longitudinal axis as it is pushed through the inserter. Most lenses, however, are made to be set within the eye in a specific orientation. Accordingly, such turning of the lens can result in the lens being placed in the eye in an improper orientation.